Water Quality

Non-point source (NPS) water pollution occurs mainly through stormwater runoff. When it rains, runoff from farmland, city streets, construction sites and suburban lawns, roofs and driveways enters our waterways. This runoff contains harmful substances such as toxics, excess nutrients and sediments. NPS pollution effects seldom show up overnight — they often go unnoticed for years. This characteristic makes it all the more difficult to control.

There are four major forms of NPS pollution: sediments, nutrients, toxic substances and pathogens.

Sediments are soil particles carried by rainwater into streams, lakes, rivers and bays. By volume, sediment is the greatest pollutant of all. It is caused mainly by erosion resulting from bare land, poor farming practices, construction and development and destabilized stream banks and channels.

Nutrients are substances which help plants and animals live and grow. NPS officials are most concerned about excessive amounts of two nutrients — nitrogen and phosphorus. Fertilizer and animal waste are the main sources of these substances.

Pathogens are disease-causing microorganisms present in human and animal waste. Most pathogens are bacteria.

The federal Clean Water Act requires all states to establish surface water quality standards for a series of pollutants and indicators, monitor surface waters for compliance with these standards, create a list of waters not meeting the standards (called the 303d impaired waters list. Click here for the latest Virginia list) and conduct a study (known as a TMDL) that identifies all contributors of the pollutant being studied along with a best case scenario as to what would be needed for cleanup to meet the standard. This is done every two years in Virginia.

Beyond that, the Commonwealth of Virginia requires that an actual implementation plan be adopted. Once an actual implementation plan is adopted, interested organizations can submit funding proposals for installing on the ground projects designed to reduce the pollutant loads. Currently, there are many streams in the District on the impaired waters list and nearly all are listed for elevated levels of E. coli bacteria. There are several implementation projects area underway, the Upper Hazel watershed, York River, Robinson River and Rapidan River.